Typically an adaptive equalizer may be used to filter and alter a signal. In some instances such an equalizer may be used to mitigate the effects of, for example, multipath propagation and/or Doppler spreading, although many other reasons to use an adaptive equalizer exist. Often an adaptive equalizer is a time variant system, meaning, in this context, that the characteristics of the system change, or are capable of changing, with time. Some examples of such adaptive equalizers may use feedback of detected symbols in addition to conventional equalization of future symbols.
Often an unwanted signal may become coupled with a desired communication signal. For example, in one embodiment, the signal powering a device may become coupled with a received communication signal. Typically the alternating-current (AC) power derived from a power outlet fluctuates at a rate of 50-60 Hz. This 50-60 Hz fluctuation may become superimposed upon a communication signal operating at a different frequency, for example, 1 GHz. A low frequency noise signal may be colloquially referred to as “hum.” In a typical case, the interfering AC signal may cause an amplitude modulation (AM) of the desired communication signal. The amplitude modulation may include the 50-60 Hz AC frequency and/or its harmonics.